Animal traps commonly operate via spring activated foot snares, and are well known devices that require a trigger mechanism to hold and then release a tension, trap-activating spring. The main prior art traps include U.S. Pat. No. 3,060,623 (Aldrich), U.S. Pat. No. 4,581,843 (Freemont), U.S. Pat. No. 5,157,863 (Godwin), CA 1,145,935 (Novak), GB 397,268 (Phelps) and my earlier international application W097/11599. Other traps capture animals by means of closing cage doors, releasing nets, physically striking the animal, etc. etc.
The trigger mechanisms for these traps invariably comprise a bar or plate that pivots around a fulcrum so as to release a tensioned activating spring, cage door, etc., when the bar or plate is depressed. However, it is necessary to construct the bar or plate as a lever in order to provide an adequate force to overcome friction generated by the compressed spring, and this requires the bar or plate to be depressed a considerable distance before the trap is triggered. This allows some animals to withdraw from the trap before or during its activation, after feeling the trigger plate give way beneath them. The animals therefore avoid capture. In addition, the pressure required to trigger these traps will vary purely on the distance between the fulcrum and the point of depression of the trigger bar or plate. This makes the trigger mechanisms inherently non-selective regarding the size and therefore species of the animal setting them off. Inevitably, this lever action also limits the length or diameter of the trigger bar or plate in that the longer the lever, the greater the depression required to trigger the trap. All of these factors limit both the efficiency and effectiveness of such traps.